Adjustable die for making transformer core laminations



F. L. PATTERSON Aug. 4, 1953 ADJUSTABLE DIE FOR MAKING TRANSFORMER CORE LAMINATIONS 3 Sheets-Sheet 2 Filed June 3, 1947 Jvwcmo FREDERICK LEROY PATTERSON mi, j@ m4 C/? A118- 4, 1953 F. l.. PATTERSON 2,647,575

ADJUSTABLE DIE FOR MAKING TRANSFORMER CORE LAMINATIONS Filed June 3, 1947 3 Sheets-Sheet 3 FREDERICK LEROY PATTERSON Patented Aug. 4,l 1953 ori-ICEY ADJUSTABLE DIE FOR MAKING TRANS- FORMER CORE LAMINATIONS Frederick Leroy Patterson; Sharon, Application J une 3, 1947, Serial No. 752,195 1 claim. (ci. 164-31) This invention relates yto improved methods for making transformer core laminations and more particularly to improved practical and economical methods for cutting the Component lamination pieces from strip stock of the electrical steel in a rapid, expeditious manner.

It has long been recognized that the reluctance of a laminated magnetic circuit is less when the grain structure of the steel runs in the direction of travel of the magnetic ux and it is, of course, Well recognized that in the process of rolling the steel the grain structure of the steel is quite definitely aligned with the direction of rolling-y Consequently in the production of magnetic cir` cuits for electrical apparatus as in the making of transformer cores, for example, it is now usual practice to so orient the steel laminations that the original direction of rolling of the steel in the pieces is made generally coincident with the direction of flow of the magnetic flux in the assembled core. This requirement as well as the additional requirement of separability for insertion of coils presents a quite complex manufacturing problem, particularly in more advanced equipment, necessitating the production and use of a large number of separate and diferently shaped lamination pieces inl producing and assembling the core. The primary object of the present invention is the provision of improved methods for cutting these lamination pieces from continuous strip stock thereof whereby all the advantages of grain-ux direction coincidence may be retained while the apparatus required for cutting the lamination pieces is relatively simple and inexpensive.

The above and other objects and advantages of the invention will become apparent upon consideration of the following detailed specification and the accompanying drawing wherein there is disclosed certain preferred embodiments of the invention.

In the drawing:

Figure l is an assembled View of a laminated transformer core of conventional design, the in-l 4 vidual pieces of which may be advantageously produced by my improved methods;

Figures 4, 5 and 6 are plan views of various of the individual pieces making up the core of Figure 1;

Figure 7 is a plan view of one of the individual pieces making up the core of Figure 3;

Figures 8 and 9 are schematic plan representations of my improved production methods for making the pieces of Figures 6 and 7, respectively;

Figures 1,0 and 11' are horizontal and vertical sections, respectively, through a die set utilized' lamination being comprised of a pair of end members I0 and Il, a pair of diagonally opposed side members I2 and I3, a second pair of diagonally opposed side members I4 and I5, and a yoke piece I6. Pieces I0 and II are identical with eachother in each lamination and insuccessive or contiguous laminations while the pieces I2 and I3 are identical in each lamination but are slightly modified in successive or contiguous Vlaminations in the manner and for the purpose to be hereinafter described. The latter is also true as regards the pieces I4 and I5 but the yoke pieces I6 are all identical, it being possible to obtain the required offset end portions simply by flopping the pieces over alternately al1 as suggested in Figure 2. As is Well understood` in the art the purpose of the offset end portions is to obtain overlapping of corresponding pieces in successive orl adjacent laminations to arrive at an assembled core which is rigid structurally and eilicient magnetically by reason of the interlocking arrangement and the abutment of the ends of the pieces with the adjacent pieces in each lamination. The general arrangement, however, readily permits of the partial assembly of the core for reception of the coil or 'coils after which the core may be completed by proper insertionl of the bridging pieces whereupon the core is rigidly riveted together as is well understood in the art.` In the core structures illustrated in Figure l, for example, the coils employed may be encircled about the yoke built up of a multiplicity of the pieces I6.

An examination of the structure of Figure l and' of the yoke piece IIi shown in Figure 6 shows that each yoke piece consists of a short strip having of the press, and guide pins 26. numeral 21 designates the male die in its enspaced parallel side edges and a pair of 'rightf angularlyrelated end edges at each end of the strip. It will be observed, further, that one end 'point of the piece is located on one `side of the longitudinal axis of thepiece while the other end point is equidistantly on the other side of the axis. This means that if any such piece is ilopped over side-for-side or end-for-end the end points will simply be transferred to the opposite sides of the longitudinal axis but will not shift axially along the direction of this axis. The longitudinal axis of the piece is shown at I1 in Figure 6 while the axes of the points are shown at I8 and I9. My improved method of producing the pieces I6 from strip stock and in substantially a continuous manner will now be described.`

Referring to Figures. 8, 10 and ll a press is shown schematically at 20 as having a bolster 2 I.

Associated with the press, either directly on the bolster or on tables suitably associated therewith are side guides 22 to guide strip stock 23 through I factured. Secured to the bolster and ram of the press is a die set having a female die assembly mounted on theplate 24 which is preferably secured to the bolster of the press, a male die assembly 25 which is'preferably secured to the ram Reference tirety and as clearly shown in Figure 10 the forward edge of this die is formed with two imear and right-angularly disposed cutting edges 28 and 5 29 to collectively cut the trailing end of each piece I8 while the rear end of the die has similarly arranged but oppositely disposed cutting edges 30 and 3I to cut the forward end of each piece I'B. The edges 28 and 30 are spaced slightly in a direction normal to their faces to allow the four straight edges representing the two rear end edges of a piece and the two forward edges of the next succeeding piece to be simultaneously cut in one operation as will be understood. A measuring stop 32 is positioned between the side guides 22 a predetermined interval beyond the die set and, of course, the female die will be constructed complementary to the male die. If now the leading end of a stock strip is fed to the press and a cropping stroke isfirst made the new end of the strip may be moved forwardly into abutting relation with the stop 32 whereby the next succeeding stroke of the press will simultaneously cut oIT from the strip one of the pieces I6, properly formed, and will simultaneously prepare (cut) the leading end of the next succeeding piece 4to be produced. In this manner I am able to produce one completed yoke piece with each stroke of the press and through the aid of automatic feed and press operation devices which are well known in this art I am able to produce these odd shaped yoke pieces at high speed and at low cost.

The general principles of my invention explained above are equally applicable for producing substantially any shape of pieceA which may be required in the production of laminated magnetic circuits. Thus in Figures 9, l2 and 13 I have shown an arrangement whereby the relatively simple pieces 33 used in making up the core of Figure 3 may be manufactured at a high rate of production and with an absolute minimum of material waste. I again employ a press-shown schematically at 34 and having a bolster 35in 4 which is mounted a die set having a male die designated in its entirety by the referencel numeral 38 and having a plan shown by the shaded area of Figure 12. It will be obvious, this die set operates upon each stroke of the press to make a 90 notch in the side edge portion of the strip and to simultaneously shear the strip transversely at a point coincident with the apex of the notch. Since only one corner of the piece 33 is eased or cut this one stroke suffices for the notching of two separate pieces and therefore to complete the production of two pieces with each stroke of the press I may provide a separate shear 31 which operates synchronously with the principal press to make a simple transverse shearingI cut 38 at the trading end of the second piece in the press. Of course, in many applications the dies for making the cut 38 may be mounted on the same set or holder which carries the die 36 so that the same press or machine is utilized for bothcperations. In operating the setup of Figure 9 theirst cropping cut will be made by the shear 31 after which the stock is moved into engagement with the stop 39 and both the press and shear operated to simultaneously produce two of the pieces 33. In this setup, as well as in the assembly of Figure 8, compressed air, rnechanical means, or other suitable expedient of which there are many in the stamping art may be utilized to remove the completed pieces upon opening of the press preparatory to the next cycle of operation.

Pieces like parts I0 and I3 of Figures l and 4 may be readily produced by the method of Figure 9 Without use, of course, of the shear 31. Similarly the pieces I4 may be produced by the method of Figure 8,` it being observed that the shape of the male die required will be identical with the shape of the space between the lefthand full line of Figure 5 and the adjacent rightangularly disposed broken lines.

In constructing the transformer core of Figure 1 it is necessary to shift longitudinally certain of the corresponding pieces in the successive laminations to secure the desired overlapping and interlocking of all the separate pieces of the core. Now to retain the rectangular solid outline or periphery of the core itwill be obvious that a corner of certain of the pieces must be clipped in alternate laminations and by way of illustration the corner to rbe clipped off the pieces I2 and I3 in alternate laminations' is indicated at 40 in Figure 4, while the corner to be clipped oil the pieces I4 and I5 in alternate laminations is indi- For varying sizes of core structures it may be desirable to have different extents of overlaps between the corresponding pieces of adjacent laminations. For example, in power transformers of smaller size an overlap of 1,/2" may be desii-able while in larger sizes an overlap of l" may be required. As regards the outer peripheral members of the core with the exception of pieces I4 and I5 this variation may be accomplished while yet using substantially standardized pieces simply by increasing the lengths of the corners 40 and 4I which are cut off standard pieces, As regards the yoke piece I6, and the pieces I4 and I5 an increase in overlap necessitates the greater olset of the points on the ends of the pieces, and

pieces I6. This die which is a modification of thel die shown in Figures 10 and 11 includes mounting plates 42 and 42 for the female portions of the die, these plates having right-angularly disposed mountingr faces 43 and 44. Since the die set is symmetrical only one symmetrical half will be specifically included in this description. Rigidly secured to the face 43 is a blade 45 the outer edge of which constitutes one of the principal shearing surfaces of the die. If the die is to be set up for cutting pieces with maximum oilset for maximum overlap (1" for example) a wide blade 46 is rigidly secured to the face 44 of the carrier 42 and, as shown, the blade 48 is notched to receive a protruding end of the blade 45. The male die which is represented by the shaded area of Figure 14 comprises a permanent section 41 represented by the vertical shading or hatching lines and a detachable blade 48 which is rigidly mounted on a mounting face 49 by means of the cap screws 50. The vertical interstice between the blades 46 and 48 represents a line of shear and as there is such an assembly on either side of the die the extent of offset of the corresponding two lines oi' shear will be lower when the blade 48 is narrow and the blade 46 wide as will be readily understood. The setup illustrated is for larger oifset and greater overlap. If less offset and less overlap is desired the blade 46 may be readily replaced with a narrower blade and the blade 48 replaced with a wider blade to bring the lines of shear inwardly to the dotted line 5i. In this manner the production equipment may be made to produce pieces of widely varying dimension while the apparatus required is kept to a minimum. It should be readily apparent that the scheme of Figure 14 may be employed with equal facility to change the offset of the point on the pointed ends of pieces I4 and I5 if this is required in the construction of the particular core being considered.

In the event that it is desirable to eliminate all possible wastage of material, even at the expense of slightly more complicated die structure. it is possible to eliminate the narrow waste area which occurs vbetween the successive punched pieces I6 of Figure 8. This is accomplished by constructing the male portion of the die of Figure 10 in a manner similar to the notch-cutting portion of the die of Figure 12. It will be understood that in this case the triangular areas of Figure 10 which are included respectively within the edges 29-30 and 28-3I will be constructed having male and female halves as does the die of Figure 12. Obviously any of the dies of my invention may be constructed in this improved manner without departing from the spirit thereof.

It should now be apparent that I have provided improved methods for producing composite pieces of electrical laminations which accomplish the objects initially set out. 'Ihrough the use of relatively simple and readily procurable tools the invention provides for the production of electrical lamination pieces in a most expeditious and economical manner and, further, provides for the production of the same in a substantially continuous and automatic manner while yet maintaining the desired coincidence of the direction of grain in the steel with the direction of magnetic flux iiow in the completed core to be assembled out of the individual pieces.

The above specifically described embodiments of the invention should be considered as illustrative only as obviously many changes may be made therein without departing from the spirit or scope of the invention. Reference should therefore be had to the appended claims in determining the scope of the invention.

What I claim is:

In a shear press for producing a plurality o identical elongated lamination members for a magnetic core from a length of elongated strip of transformer steel wherein the direction of ilux iiow is to be longitudinally along said member and with the grain structure of the member, said press being adapted to receive said length of lamination steel strip to form lamination member having similarly shaped pointed ends spaced inwardly from the edges of the strip, with the apices of said points being disposed on opposite sides of the longitudinal center line of the member, a die member for simultaneously forming the laterally and longitudinally offset ends of adjacent members comprising adjustable side guides for slidably engaging the edges of the steel strips, a pair of longitudinally disposed V-shaped female shear die parts, the apices of said female die parts being on opposite sides of the longitudinal center line of the path of travel of the strip to be sheared, a pair of shear blades xed on the adjacent parallel faces of said female die parts, the adjacent ends of said blades being in spaced parallel, side by side relation, a second pair of shear blades mounted transversely to said first mentioned shear blades, said blades forming V-shaped cutting dies with their apices in offset, spaced, side by side relation, a pair of laterally spaced longitudinally offset V-shaped male die parts, a single offset shear blade secured on one pair of parallel faces of said male die parts, said oiset shear blade including a narrow central portion snugly fitting between the spaced parallel ends of the first mentioned shear blades secured on said female parts, the opposed surfaces of said narrow central part being a continuous part of the cutting edges of said offset shear blade, the offset portion of said offset shear blade being a continuation of the transverse surface of the V-shaped male die, a pair of shear blades secured on said other pair of male die surfaces, said last mentioned shear blades engaging in shearing relation with the transverse shear blades of the female die parts, said first and last mentioned transverse shear blades being of different thickness whereby said male and female blades may be interchanged to vary the oiset of the apices of the die parts.

FREDERICK LEROY PATTERSON.

References cited in che me of this patent UNITED STATES PATENTS Number Name Date 649,112 Smith May 8, 1900 958,459 Ames May 17, 1910 1,288,491 Bowen Dec. 24, 1918 1,339,990 Troy May 11, 1920 1,356,178 Thordarson Oct. 19, 1920 1,772,785 Smith Aug. l2, 1930 1,802,502 Doyle Apr. 28, 1931 1,913,119 Joachimczyk June 6, 1933 2,330,824 Granfield Oct. 5. 1943 2,388,115 Brooks Oct. 30, 1945 2,456,461 Dunn Dec. 14, 1948 

